Expressing class I wheat NHX (TaNHX2) gene in eggplant (Solanum melongena L.) improves plant performance under saline condition

Abstract

Brinjal or eggplant (Solanum melongena L.) is an important solanaceous edible crop, and salt stress adversely affects its growth, development, and overall productivity. To cope with excess salinity, vacuolar Na⁺/H⁺ antiporters provide the best mechanism for ionic homeostasis in plants under salt stress. We generated transgenic eggplants by introducing wheat TaNHX2 gene that encodes a vacuolar Na⁺/H⁺ antiporter in to the eggplant genome via Agrobacterium-mediated transformation using pBin438 vector that harbors double35S:TaNHX2 to confer salinity tolerance. Polymerase chain reaction and southern hybridization confirmed the presence and integration of TaNHX2 gene in T₁ transgenic plants. Southern positive transgenic eggplants showed varied levels of TaNHX2 transcripts as evident by RT-PCR and qRT-PCR. Stress-inducible expression of TaNHX2 significantly improved growth performance and Na⁺ and K⁺ contents from leaf and roots tissues of T₂ transgenic eggplants under salt stress, compared to non-transformed plants. Furthermore, T₂ transgenic eggplants displayed the stable leaf relative water content and chlorophyll content, proline accumulation, improved photosynthetic efficiency, transpiration rate, and stomatal conductivity than the non-transformed plants under salinity stress (200 mM NaCl). Data showed that the T₂ transgenic lines revealed that reduction in MDA content, hydrogen peroxide, and oxygen radical production associated with the significant increase of antioxidant enzyme activity in transgenic eggplants than non-transformed plants under salt stress (200 mM NaCl). This study suggested that the TaNHX2 gene plays an important regulatory role in conferring salinity tolerance of transgenic eggplant and thus may serve as a useful candidate gene for improving salinity tolerance in other vegetable crops.

Keywords: Salt stress; Solanum melongena; TaNHX2; Vegetables.